1. Technical Field
This invention relates generally to procedures and equipment for stopping an existing water, sewer, gas, or other line containing fluid under pressure, and more particularly to a valve assembly and installation method for inserting a valve in a line without otherwise shutting down the line during the insertion.
2. Description of Related Art
The task of inserting a valve in a line containing fluid under pressure (e.g., a municipal water line or natural gas line) without otherwise shutting down the line during the insertion can be expensive, inconvenient, and time consuming. Yet the need to do so is commonplace. Damaged fire hydrants, for example, frequently need replacement and doing so quickly in a cost-effective manner often involves shutting down water service while a valve is inserted in a water line branch feeding the fire hydrant.
One existing way of inserting a valve into a fire hydrant water line or other line without shutting down service proceeds by cutting a hole in the pipe with a known type of hot-tapping hole saw apparatus. A valving apparatus is then added that forces a rubber plunger into the hole. The rubber plunger expands enough to block the line. Withdrawing the plunger unblocks the line.
One problem with the rubber plunger technique is that success of the valving apparatus depends on the internal size and condition of the pipe. In addition, an old, corroded or otherwise damaged and weakened pipe is subject to being broken. Furthermore, pushing a plug through a tapped hole subjects the rubber gate to being cut by the sharp edges of the hole cut in the pipe each time the gate is opened and closed. For those and other reasons that will become more apparent, users need a better way to insert a valve in a water line or other line containing fluid under pressure.